Selective reduction of nitrate to nitrogen gas with hydrating electrons from the photo-corrosion of natural pyrite

•Natural pyrite was used to generate eaq− by photo-corrosion.•NO3− reduction by the pyrite/UV process was studied.•98.07% NO3− reduction efficiency and 98.61% N2 selectivity were achieved.•eaq− was identified as the main species for the selective reduction of NO3− to N2.•A possible denitrification mechanism of the pyrite/UV process was tentatively proposed.